In what way did the Enlightenment lay the foundations of the modern world? Are these changes positive or negative?

The Enlightenment laid the foundations for our modern world in that it moved us towards a society based more on ideas of reason and science than on religious faith.  Before the Enlightenment, the Bible was seen as the definite authority about all questions.  This meant that people were not all that interested in reasoning questions out for themselves.

With the Enlightenment, came an emphasis on proving things scientifically.  People started to be more interested in finding out how the world worked; discovering physical laws by which the universe ran.  This change allowed us to have the sort of technologically-based society we now have.

As far as whether this is positive or negative, you'd have to ultimately decide for yourself.  I imagine the positives of all our scientific knowledge are fairly clear.  In terms of negatives, you might argue that a loss of religious faith is a negative.  Or you might argue that technology has had a harmful effect on human relationships.